Washington-East Washington Joint Authority - Executive Summary |
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A. The Washington-East Washington Joint Authority's (WEWJA) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to. The WEWJA emergency response policy involves the preparation of response plans which are tailored to each facility and to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program requirements. B. The WEWJA Chlorination System has been installed to disinfect the flow in Chartiers Creek. The chlorination station is located on Arden Station Road within the treatment plant. The station includes a chlorination room, which contains liquid chlorine containers, a chlorinator, and various safety equipment, and an instrument room which contains a flow recorder, various electrical panels, and additional safety equipment. The amo unt of chlorine handled is a one-ton container. The facility is normally unmanned. Wastewater treatment operators visit the facility daily and respond to any trouble alarms which may occur. C. The off-site consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative Scenario". The first scenario is defined by EPA, which states that "the owner or operator shall assume that the ... maximum quantity in the largest vessel... is released as a gas over 10 minutes, " due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst case release scenario". Atmospheric dispersion modeling has to be performed to determine the distance traveled by the chlorine released before its concentration decreases to the "toxic endpoint" selected by EPA of 3 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). This is defined by the American Industrial Hygiene Associati on (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair and individual's ability to take protective action." The residential population within a circle with a radius corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected". The worst-case release scenario at WEWJA involves a failure of a one-ton container (a total of 2,000 lb of chlorine). The offsite consequence analysis for this scenario was performed for two sets of conditions. The first set followed conditions pre-defined by EPA, namely release of the entire amount as a gas in 10 minutes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. EPA set thes e conditions to facilitate the performance of the offsite consequence analysis; EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, average temperature (77 F), and average humidity (50%) were used for both sets. When atmospheric dispersion modeling for the worst case scenario was performed using the EPA assumptions, a distance to toxic endpoint 7.4 miles and an estimate of residential population potentially affected 47,000 was obtained. The alternative release scenario involves a 1" X 1" puncture in the side of the one-ton container. The amount of chlorine over one hour (the duration of the release 1559 lb/min. Toxic endpoint distances to ERPG-2 levels were obtained. (Defined by AIHA as "the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experience or developing life-threatening health effects".) The typical meteorological conditions used were Stability D, wind speed 3.0 m/s, average air temperature (77 F), and average humidity (50%) . The estimated distances traveled to the toxic endpoints are 1.4 miles with an estimate of 31,000 residential population affected. D. The general WEWJA release prevention program is based on the following key elements: * High level of training of the operators * Preventive maintenance program * Use of state-of-the-art process and safety equipment * Use of accurate and effective operating procedures, written with the participation of the operators * Performance of a hazard review of equipment and procedures * Implementation of an auditing and inspection program Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), worn by the operators during connection/disconnections of chlorine supply, awareness of the hazardous and toxic properties of chlorine, and presence of chlorine detectors. E. No accidental releases of chlorine have occurred at this facility in the p ast five years. F. The facility has an emergency response program, which has been coordinated (reviewed) by the local fire department, which is a member of the Local Emergency Response Planning Committee (LEPC). This program includes an emergency response decision tree and a notification plan. Emergency response drills and drill evaluations are conducted every six months; emergency operation and response procedures are also reviewed at that time. |